In this article we will discuss about difference between gram positive and gram negative bacteria
Difference Between Gram Positive and Gram Negative Bacteria
1. Cell Wall Structure: Gram positive bacteria have a thick peptidoglycan layer in their cell wall, which retains the crystal violet stain during the staining process. In contrast, gram-negative bacteria have a thin peptidoglycan layer and an additional outer membrane composed of lipopolysaccharides (LPS) that makes them impermeable to the crystal violet stain.
2. Staining: Gram positive bacteria retain purple color of crystal violet stain, while gram-negative bacteria do not and instead take up the counterstain safranin, which gives them a pink or red color.
3. Lipopolysaccharides (LPS): Gram-negative bacteria possess LPS in their outer membrane, which consists of lipid A, core polysaccharide, and O-specific polysaccharide. LPS acts as an endotoxin and contributes to the virulence of gram-negative bacteria.
4. Porins: Gram-negative bacteria have porin proteins in their outer membrane, which form channels for the transport of molecules across the membrane. Gram-positive bacteria lack an outer membrane and do not possess porins.
5. Antibiotic Susceptibility: Gram-positive bacteria are generally more susceptible to antibiotics than gram-negative bacteria due to the differences in their cell wall structure. The thick peptidoglycan layer in gram-positive bacteria makes them more susceptible to cell wall targeting antibiotics, while the outer membrane of gram-negative bacteria acts as a barrier against many antibiotics.
6. Toxins: Gram-negative bacteria produce endotoxins, which are released upon cell lysis, while gram-positive bacteria produce exotoxins, which are secreted by the bacteria and can cause damage to host cells.
7. Sensitivity to Lysozyme: Lysozyme, an enzyme found in tears, saliva, and other body fluids, can break down the peptidoglycan layer in bacterial cell walls. Gram-positive bacteria are more sensitive to lysozyme due to their thick peptidoglycan layer, while gram-negative bacteria are more resistant to its action.
8. Resistance to Drying: Gram-positive bacteria have a higher resistance to drying compared to gram-negative bacteria due to the presence of a thick peptidoglycan layer that helps retain water.
9. Outer Membrane Permeability: Gram-negative bacteria have a higher outer membrane permeability than gram-positive bacteria due to the presence of porins and other transport proteins. This allows gram-negative bacteria to take up a wider range of nutrients and molecules from their environment.
10. Pathogenicity: Both gram-positive and gram-negative bacteria can be pathogenic, but gram-negative bacteria are generally considered more virulent. The presence of endotoxins in gram-negative bacteria and the ability to evade host immune responses through various mechanisms contribute to their pathogenicity.
Summary : Difference between gram positive and gram negative bacteria
- Gram-positive bacteria have a thick peptidoglycan layer in their cell wall, while gram-negative bacteria have a thin peptidoglycan layer and an outer membrane.
- Gram-positive bacteria retain the purple color of the crystal violet stain, while gram-negative bacteria take up the pink or red color of the counterstain.
- Gram-negative bacteria possess lipopolysaccharides (LPS) in their outer membrane, while gram-positive bacteria do not.
- Gram-negative bacteria have porins in their outer membrane, while gram-positive bacteria lack an outer membrane and porins.
- Gram-positive bacteria are generally more susceptible to antibiotics than gram-negative bacteria.
- Gram-negative bacteria produce endotoxins, while gram-positive bacteria produce exotoxins.
- Gram-positive bacteria are more sensitive to lysozyme, while gram-negative bacteria are more resistant.
- Gram-positive bacteria have higher resistance to drying than gram-negative bacteria.
- Gram-negative bacteria have higher outer membrane permeability than gram-positive bacteria.
- Gram-negative bacteria are generally considered more virulent than gram-positive bacteria.
Read More:Cell Biology Notes